/*
CSE 303, Spring 2009, Marty Stepp
This program has various functions related to getting/setting bits.
*/

#include <stdio.h>
#include <stdbool.h>

int get_bit(int n, int b);
void print_binary(int n);
int set_bit(int n, int b, int value);

// 119 => 1110111
// get_bit(119, 3)
// (119 >> 3) => 1110
// (119 >> 3) & 1 => 0

// Returns the value of the b'th least significant bit of integer n.
// pre: 0 <= b <= 31
int get_bit(int n, int b) {
    return ((n >> b) & 1);
}

// turn on bit #b
// n = 119 => 1110111
// set_bit(n, b=3) ==> 127
// n | b
// (119 | 2^3)

// Sets the b'th least significant bit of integer n to the given value.
// pre: 0 <= b <= 31,  and 0 <= value <= 1
int set_bit(int n, int b, int value) {
    int bit = 1 << b;  // b=3 --> bit= 1000  (8)

    if (value == 1) {
        // turn on bit b
        return n | bit;
    } else {
        // turn off bit b
        // bit2 = 11111111111111111111111110111
        // n & bit2
        return n & ~bit;
    }
}

// 42 --> 00000000000000000000000000101010
//        ^
//         ^
//          ^
// Prints the given integer in binary.
void print_binary(int n) {
    int i;
    bool seen1 = false;
    for (i = 31; i >= 0; i--) {
        if (get_bit(n, i) == 0) {
            if (seen1) {
                printf("0");
            }
        } else {
            seen1 = true;
            printf("1");
        }
    }
    printf("\n");
}

int main(void) {
    int x1 = 42;        // 101010
    print_binary(x1);

    x1 = set_bit(x1, 0, 1);
    print_binary(x1);
    printf("%d\n", x1);
    
    x1 = set_bit(x1, 4, 1);
    print_binary(x1);
    printf("%d\n", x1);
    
    x1 = set_bit(x1, 13, 1);
    print_binary(x1);
    printf("%d\n", x1);
    
    x1 = set_bit(x1, 5, 0);
    print_binary(x1);
    printf("%d\n", x1);
    
    return 0;
}